fix typo in fold (thanks Georg Schmid)

Author: leafo

moon/init.lua

@@ -154,7 +154,7 @@ fold = function(items, fn)
   if len > 1 then
     local accum = fn(items[1], items[2])
     for i = 3, len do
-      accum = fn(acum, items[i])
+      accum = fn(accum, items[i])
     end
     return accum
   else

moon/init.moon

@@ -129,7 +129,7 @@ fold = (items, fn)->
   if len > 1
     accum = fn items[1], items[2]
     for i=3,len
-      accum = fn acum, items[i]
+      accum = fn accum, items[i]
     accum
   else
     items[1]